Pflanzenkrankheiten. 199 



The same organism occurs in the greatest abundance in the soil 

 and on the roots of many plants, but the anatomical structure of 

 the Underground portions of the majority of them is not of a nature 

 to expose the cambium layers, through lenticels or otherwise, and 

 they, therefore, escape scab formation even though covered exter- 

 nally by growths of the same organism. Its parasitism is dependent 

 on ä particular type of root or tuber structure and when this is not 

 present it is forced to live as a saprophyte. According to the authors, 

 the explanation of scabbing of the potato and beet, while many 

 other root and tuber plants escape, undoubtedl}^ lies in the fact that 

 some sort of a cambium — either already present or easily regene- 

 rated — is so close to the surface that the toxic substances produced 

 by these thread bacteria readily affect it. 



The damages and changes in anatomical structure of the sugar 

 beet, caused by beet scab are described in detail and figured. 



M. J. Sirks (Haarlem). 



Rogers, J. T. and G. F. Gravatt. Notes on the chestnut 

 bark disease. (Phytopathology. V. p. 45—47. 1915.) 



In Virginia the chinquapin in the vicinity of infections of the 

 chestnut bark disease being very rarely diseased, the authors have 

 made artificial inoculations on 61 chinquapins in a patch near 

 Leesburg; they found that the chinquapin in Virginia has no 

 more resistance to the girdling growth of the blight fungus than 

 has the chestnut. Hower, the chinquapin does not have as many 

 insect and other injuries; this is, according to the authors, probably 

 reason for its freedom from the disease in the field. 



Measuring the increase from year to year in a cankered or 

 sporeproducing area in a woodlot, the authors found the number 

 of cankers in a plot of trees rising in one years time from 58 to 

 199, the number of diseased trees from 40 to 83 (out of 140 trees). 

 Variations in many factors (percentage of chestnut; density of the 

 stand; size and condition of the trees; temperature and moisture 

 conditions) make accurate comparisons between infections in different 

 sections of the country difficult. The average rate ofdiameter growth 

 of the disease cankers was measured 6.53 inches a year; it would 

 therefore require a number of years for a single canker to girdle 

 a large tree; by collaboration of 3 or 4 separate cankers this result 

 is reached in a much shorter time. M. J. Sirks (Haarlem). 



Rumbold, C, Notes on Chestnut fruits infected with the 

 chestnut blight fungus. (Phytopathology. V. p. 64 — 65. 1915.) 



The researches of Miss Rumbold about the infection of chest- 

 nut fruits by the blight fungus gave interesting results: 



A large number of fresh sound nuts and of burs containing 

 nuts were collected in a blight-infested chestnut orchard in October 

 1913, and cut open in January 1914. The nuts which had remained 

 in the bur formed a large majority of the infected fruits. The burs 

 were the source of infection. The fungus grew from the infected 

 bur through the shell at the base of the nut where there is a close 

 connection between the two and where the hard shell of the nut 

 matures last. Orange colored mycelium showed in patches on the 

 Shell around the base of the nuts. Those infected nuts found outside 



